Its name is Erg Chech 002, but scientists refer to it as EC 002 for short. It was discovered in 2020 in the Sahara Desert and is the oldest known example of space magma. Its age, almost 4.6 billion years, indicates that this meteorite is, in fact, even older than Earth.
According to a new study published in the Proceedings of the National Academy of Sciences, this primordial rock, the only one of its kind found so far, formed at the same time as the Solar System as part of a larger rocky body on the way to becoming a new planet. It is, therefore, a rare fragment that managed to survive the destruction of a protoplanet, likely being absorbed by a larger planetary body in the midst of formation.
In May 2020, several pieces of EC 002 were found near the Algerian town of Adrar, and according to the Lunar and Planetary Institute (LPI) description, the fragments were “relatively coarse-grained, tan and beige,” sporadically studded with crystals that were “larger, green, greenish-yellow, and less commonly brownish-yellow.”
A meteorite is an achondrite, a rock that has undergone a melting process in the body from which it originated and was once part of a much larger object, with a distinct crust and core. Achondrites account for only 71% of the meteorites that fall on our planet, unlike chondrites, which are much more abundant (almost 86% of the total) and have not undergone melting in their parent bodies.
According to the researchers, approximately 3,100 known meteorites originated in the crust and mantle layers of rocky asteroids, but they reveal very little about the variety and diversity of protoplanets during the Solar System's early life. Nearly 95% of these, in fact, were born from just two "parent" bodies, with 75% originating from asteroid 4 Vesta, the third largest in the asteroid belt, with a diameter of about 530 km.
That's why, among the thousands of known stony meteorites, EC 002 stands out like a beacon in the night. Analysis of the aluminum and magnesium isotopes present in the rock indicates that the "parent" of this unique meteorite was an extraordinarily old body, about 4.566 billion years old. And its chemical composition reveals that it emerged from a reservoir of partially molten magma in the parent body's crust.
"This meteorite," the researchers write, "is the oldest igneous rock analyzed to date and sheds light on the formation of the primordial crusts that covered the earliest protoplanets."
"It is reasonable to assume," the study authors continue, "that many similar dendritic bodies accreted at the same time and were also covered by the same type of primordial crust." However, when the scientists compared the wavelength patterns of light reflected by EC 002 with that of 10,000 other known objects, they found no matches. "EC 002," the researchers note, "was clearly distinguishable from all other asteroid groups. To date, no object with similar spectral characteristics has been identified."
The absence of objects similar to EC 002 leads researchers to believe that, at the time the planets in our system were forming, most protoplanetary bodies similar to the one that gave rise to this meteorite never made it past their infancy. According to the study, they most likely broke into pieces in collisions with other objects, or were absorbed by larger, more successful rocky planets, such as Earth, Mars, Venus, and Mercury, leaving very little material capable of generating meteorites like EC 002.
A rock, then, older than Earth itself and once part of a 'candidate planet' that failed to survive the violence of a rapidly forming Solar System.